If you are returning to work, then that is maybe something to consider in terms of the timing. How you go about it can vary, and it depends on the child.
My first was never good at latching on, we struggled with it for about 6 weeks, then introduced a bottle with breast milk, my milk dried up quickly though and he was on bottles of formula after that.
My second breastfed really well, but was a nightmare to get onto bottles of either breastmilk or formula and wouldn't take either from a cup. We started at about 4 months as I was intending going back to work at 5 months, but I had to delay until 6 months as he would not take any milk other than from the breast. we had to wait until he had established a good routine with his solids and started to deny him milk for longer and longer during the day, but offered him a bottle. He finally took it the day before I was due back! This was when a HV recommended cheap latex teats rather than the expensive silicone ones - they are much softer in their mouth.
I continued to breasfeed him before and after work and he had a bottle of formula during the day for a while.
Good luck